MnO/C core-shell nanorods as high capacity anode materials for lithium-ion batteries

MnO/C core-shell nanorods were synthesized by an in situ reduction method using MnO₂ nanowires as precursor and block copolymer F127 as carbon source. Field emission scanning electron microscopy and transmission electron microscopy analysis indicated that a thin carbon layer was coated on the surfaces of the individual MnO nanorods. The electrochemical properties were evaluated by cyclic voltammetry and galvanostatic charge-discharge techniques. The as-prepared MnO/C core-shell nanorods exhibit a higher specific capacity than MnO microparticles as anode material for lithium ion batteries.     

Enhanced electrochemical performance of porous NiO-Ni nanocomposite anode for lithium ion batteries

The nickel foam-supported porous NiO-Ni nanocomposite synthesized by electrostatic spray deposition (ESD) technique was investigated as anodes for lithium ion batteries. This anode was demonstrated to exhibit improved cycle performance as well as good rate capability. Ni particles in the composites provide a highly conductive medium for electron transfer during the conversion reaction of NiO with Li⁺ and facilitate a more complete decomposition of Li₂O during charge with increased reversibility of conversion reaction. Moreover, the obtained porous structure is benefical to buffering the volume expansion/constriction during the cycling.     

Carbon-coated SiO2 nanoparticles as anode material for lithium ion batteries

A simple approach is proposed to prepare C-SiO₂ composites as anode materials for lithium ion batteries. In this novel approach, nano-sized silica is soaked in sucrose solution and then heat treated at 900 °C under nitrogen atmosphere. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis shows that SiO₂ is embedded in amorphous carbon matrix. The electrochemical test results indicate that the electrochemical performance of the C-SiO₂ composites relates to the SiO₂ content of the composite. The C-SiO₂ composite with 50.1% SiO₂ shows the best reversible lithium storage performance. It delivers an initial discharge capacity of 536 mAh g⁻¹ and good cyclability with the capacity of above 500 mAh g⁻¹ at 50th cycle. Electrochemical impedance spectra (EIS) indicates that the carbon layer coated on SiO₂ particles can diminish interfacial impedance, which leads to its good electrochemical performance.     

One-dimensional nanostructures as electrode materials for lithium-ion batteries with improved electrochemical performance

One-dimensional (1D) nanosize electrode materials of lithium iron phosphate (LiFePO₄) nanowires and Co₃O₄–carbon nanotube composites were synthesized by the hydrothermal method. The as-prepared 1D nanostructures were structurally characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. We tested the electrochemical properties of LiFePO₄ nanowires as cathode and Co₃O₄–carbon nanotubes as anode in lithium-ion cells, via cyclic voltammetry and galvanostatic charge/discharge cycling. LiFePO₄ nanorod cathode demonstrated a stable performance over 70 cycles, with a remained specific capacity of 140 mAh g⁻¹. Nanocrystalline Co₃O₄–carbon nanotube composite anode exhibited a reversible lithium storage capacity of 510 mAh g⁻¹ over 50 cycles. 1D nanostructured electrode materials showed strong potential for lithium-ion batteries due to their good electrochemical performance.     

Solvothermal synthesis of hierarchical LiFePO4 microflowers as cathode materials for lithium ion batteries

Hierarchical LiFePO₄ microflowers have been successfully synthesized via a solvothermal reaction in ethanol solvent with the self-prepared ammonium iron phosphate rectangular nanoplates as a precursor, which is obtained by a simple water evaporation method beforehand. The hierarchical LiFePO₄ microflowers are self-assemblies of a number of stacked rectangular nanoplates with length of 6-8 μm, width of 1-2 μm and thickness of around 50 nm. When ethanol is replaced with the water-ethanol mixed solvent in the solvothermal reaction, LiFePO₄ micro-octahedrons instead of hierarchical microflowers can be prepared. Then both of them are respectively modified with carbon coating through a post-heat treatment and their morphologies are retained. As a cathode material for rechargeable lithium ion batteries, the carbon-coated hierarchical LiFePO₄ microflowers deliver high initial discharge capacity (162 mAh g⁻¹ at 0.1 C), excellent high-rate discharge capability (101 mAh g⁻¹ at 10 C), and cycling stability, which exhibits better electrochemical performances than carbon-coated LiFePO₄ micro-octahedrons. These enhanced electrochemical properties can be attributed to the hierarchical micro/nanostructures, which can take advantage of structure stability of micromaterials for long-term cycling. Furthermore the rectangular nanoplates as the building blocks can improve the electrochemical reaction kinetics and finally promote the rate performance.     

Li3V2(PO4)3/C composite as an intercalation-type anode material for lithium-ion batteries

The carbon coated monoclinic Li₃V₂(PO₄)₃ (LVP/C) powder is successfully synthesized by a carbothermal reduction method using crystal sugar as the carbon source. Its structure and physicochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy and electrochemical methods. The LVP/C electrode exhibits stable reversible capacities of 203 and 102 mAh g⁻¹ in the potential ranges of 3.0-0.0 V and 3.0-1.0 V versus Li⁺/Li, respectively. It is identified that the insertion/extraction of Li⁺ undergoes a series of two-phase transition processes between 3.0 and 1.6 V and a single phase process between 1.6 and 0.0 V. The ex situ XRD patterns of the electrodes at various lithiated states indicate that the monoclinic structure can still be retained during charge-discharge process and the insertion/deinsertion of lithium ions occur reversibly, which provides an excellent cycling stability with high energy efficiency.     

Fe3O4 submicron spheroids as anode materials for lithium-ion batteries with stable and high electrochemical performance

A magnetite (Fe₃O₄) powder composed of uniform sub-micrometer spherical particles has been successfully synthesized by a hydrothermal method at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and galvanostatic cell cycling are employed to characterize the structure and electrochemical performance of the as-prepared Fe₃O₄ spheroids. The magnetite shows a stable and reversible capacity of over 900 mAh g⁻¹ during up to 60 cycles and good rate capability. The experimental results suggest that the Fe₃O₄ synthesized by this method is a promising anode material for high energy-density lithium-ion batteries.     

A novel CuO-nanotube/SnO2 composite as the anode material for lithium ion batteries

A novel CuO-nanotubes/SnO₂ composite was prepared by a facile solution method and its electrochemical properties were investigated as the anode material for Li-ion battery. The as-prepared composite consisted of monoclinic-phase CuO-nanotubes and cassiterite structure SnO₂ nanoparticles, in which SnO₂ nanoparticles were dramatically decorated on the CuO-nanotubes. The composite showed higher reversible capacity, better durability and high rate performance than the pure SnO₂. The better electrochemical performance could be attributed to the introducing of the CuO-nanotubes. It was found that the CuO-nanotubes were reduced to metallic Cu in the first discharge cycle, which can retain tube structure of the CuO-nanotubes as a tube buffer to alleviate the volume expansion of SnO₂ during cycling and act as a good conductor to improve the electrical conductivity of the electrodes.     

Electrostatic spray deposition of porous Fe2O3 thin films as anode material with improved electrochemical performance for lithium-ion batteries

Iron oxide materials are attractive anode materials for lithium-ion batteries for their high capacity and low cost compared with graphite and most of other transition metal oxides. Porous carbon-free α-Fe₂O₃ films with two types of pore size distribution were prepared by electrostatic spray deposition, and they were characterized by X-ray diffraction, scanning electron microscopy and X-ray absorption near-edge spectroscopy. The 200 °C-deposited thin film exhibits a high reversible capacity of up to 1080 mAh g⁻¹, while the initial capacity loss is at a remarkable low level (19.8%). Besides, the energy efficiency and energy specific average potential (E_av) of the Fe₂O₃ films during charge/discharge process were also investigated. The results indicate that the porous α-Fe₂O₃ films have significantly higher energy density than Li₄Ti₅O₁₂ while it has a similar E_av of about 1.5 V. Due to the porous structure that can buffer the volume changes during lithium intercalation/de-intercalation, the films exhibit stable cycling performance. As a potential anode material for high performance lithium-ion batteries that can be applied on electric vehicle and energy storage, rate capability and electrochemical performance under high-low temperatures were also investigated.     

Silicon nanowires coated with copper layer as anode materials for lithium-ion batteries

Silicon nanowires (Si NWs) with copper-coating as high capacity and improved cycle-life anode for lithium-ion batteries have been successfully prepared by chemical vapor deposition and magnetron sputtering methods. The morphology, structure, composition as well as the electrochemical performance of copper-coated Si NWs is characterized in detail. The results indicate that the copper-coated Si NWs electrodes show an initial coulombic efficiency of 90.3% when cycling between 0.02 V and 2.0 V (versus Li/Li⁺) at a current density of 210 mA g⁻¹. The copper-coated Si NWs electrodes exhibit a capacity as high as 2700 mAh g⁻¹ at the first cycle. They also show a good capacity retention and excellent rate capability compared with pristine and carbon-coated Si NWs.     

Synthesis and electrochemical performances of core-shell structured Li[(Ni1/3Co1/3Mn1/3)0.8(Ni1/2Mn1/2)0.2]O2 cathode material for lithium ion batteries

Micro-scale core-shell structured Li[(Ni_1/3Co_1/3Mn_1/3)_0.8(Ni_1/2Mn_1/2)_0.2]O₂ powders for use as cathode material are synthesized by a co-precipitation method. To protect the core material Li[Ni_1/3Co_1/3Mn_1/3]O₂ from structural instability at high voltage, a Li[Ni_1/2Mn_1/2]O₂ shell, which provides structural and thermal stability, is used to encapsulate the core. A mixture of the prepared core-shell precursor and lithium hydroxide is calcined at 770 °C for 12 h in air. X-ray diffraction studies reveal that the prepared material has a typical layered structure with an space group. Spherical morphologies with mono-dispersed powders are observed in the cross-sectional images obtained by scanning electron microscopy. The core-shell Li[(Ni_1/3Co_1/3Mn_1/3)_0.8(Ni_1/2Mn_1/2)_0.2]O₂ electrode has an excellent capacity retention at 30 °C, maintaining 99% of its initial discharge capacity after 100 cycles in the voltage range of 3-4.5 V. Furthermore, the thermal stability of the core-shell material in the highly delithiated state is improved compared to that of the core material. The resulting exothermic onset temperature appear at approximately 272  °C, which is higher than that of the highly delithiated Li[Ni_1/3Co_1/3Mn_1/3]O₂ (261 °C).     

Electrochemical performances of BiSbO4 as electrode material for lithium batteries

We present an electrochemical study of BiSbO₄, an opened layered oxide having a structure related to Aurivillius phases. Li//BiSbO₄ cells show a large specific capacity as high as 1250 mAh g⁻¹ during reduction down to 0.5 V. This reaction involves 18Li atoms per formula unit, pointing it towards a very promising cathode material for primary lithium batteries, in particular for ICD devices. The characterization of the reduction products indicates that the reduction of BiSbO₄ with lithium presumably goes along firstly with the formation of metallic Sb and Bi to follow the formation of the alloys Li₃Bi and Li₃Sb dispersed in a lithium oxide matrix. In situ X-ray diffraction experiments proved the amorphous nature of both metals and final alloys. On the other hand when Li//BiSbO₄ cells are limited to discharge down to 1.2 V, BiSbO₄ reacts with 5Li atoms. After the first discharge, that develops a specific capacity of 350 mAh g⁻¹, high cyclability has been observed.     

Synthesis, structure and electrochemical Li insertion behaviour of Li2Ti6O13 with the Na2Ti6O13 tunnel-structure

Li₂Ti₆O₁₃ has been prepared from Na₂Ti₆O₁₃ by Li ion exchange in molten LiNO₃ at 325 °C. Chemical analysis and powder X-ray diffraction study of the reaction product respectively indicate that total Na/Li exchange takes place and the Ti-O framework of the Na₂Ti₆O₁₃ parent structure is kept under those experimental conditions. Therefore, Li₂Ti₆O₁₃ has been obtained with the mentioned parent structure. An important change is that particle size is decreased significantly which is favoring lithium insertion. Electrochemical study shows that Li₂Ti₆O₁₃ inserts ca. 5 Li per formula unit in the voltage range 1.5-1.0 V vs. Li⁺/Li, yielding a specific discharge capacity of 250 mAh g⁻¹ under equilibrium conditions. Insertion occurs at an average equilibrium voltage of 1.5 V which is observed for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. However, a capacity loss of ca. 30% is observed due to a phase transformation occurring during the first discharge. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g⁻¹ at C/12) and retained upon cycling. Taking into consideration these results, we propose Li₂Ti₆O₁₃ as an interesting material to be further investigated as the anode of lithium ion batteries.     

Fe and Ni impurity distribution and electrochemical performance of LiCoO2 electrode materials for lithium ion batteries

The distribution of Fe³⁺ and Ni³⁺ impurities and the electrochemical performance of LiCoO₂ electrodes were examined. Commercial LiCoO₂ powders supplied by Aldrich were used. The electrochemical performance of LiCoO₂ was modified by rotor blade grinding of LiCoO₂ followed by thermal treatment. Structural information on Fe³⁺ and Ni³⁺ impurities was obtained using both conventional X-band and high-frequency electron paramagnetic resonance spectroscopy (EPR). It was found that Fe³⁺ occupies a Co-site having a higher extent of rhombic distortion, while Ni³⁺ is in a trigonally distorted site. After rotor blade grinding of LiCoO₂, isolated Fe³⁺ ions display a tendency to form clusters, while isolated Ni³⁺ ions remain intact. Re-annealing of ground LiCoO₂ at 850 °C leads to disappearance of iron clusters; isolated Fe³⁺ ions are recovered. The electrochemical performance of LiCoO₂ was discussed on the basis of isolated and clustered ions.     

Synthesis and electrochemical performance of Li2CoSiO4 as cathode material for lithium ion batteries

Li₂CoSiO₄ has been prepared successfully by a solution route or hydrothermal reaction for the first time, and its electrochemical performance has been investigated primarily. Reversible extraction and insertion of lithium from and into Li₂CoSiO₄ at 4.1 V versus lithium have shown that this material is a potential candidate for the cathode in lithium ion batteries. At this stage reversible electrochemical extraction was limited to 0.46 lithium per formula unit for the Li₂CoSiO₄/C composite materials, with a charge capacity of 234 mAh g⁻¹ and a discharge capacity of 75 mAh g⁻¹.     

Preparation and electrochemical properties of TiO2 hollow spheres as an anode material for lithium-ion batteries

TiO₂ hollow spheres are fabricated by a sol-gel process using carbon spheres as template. The diameter and the shell thickness of the TiO₂ hollow spheres are about 400-600 nm and 60-80 nm, respectively. The electrochemical properties of the hollow spheres are investigated by galvanostatic cycling and cyclic voltammetry (CV) measurements. The initial discharge capacity reaches 291.2 mAh g⁻¹ at a current density of 60 mA g⁻¹. The average discharge capacity loss is about 1.72 mAh g⁻¹ per cycle from the 2nd to the 40th cycles and the coulombic efficiency is approximately 98% after 40 cycles, indicating excellent cycling stability and reversibility.     

Improvement of electrochemical behavior of Sn2Fe/C nanocomposite anode with Al2O3 addition for lithium-ion batteries

Sn₂Fe/Al₂O₃/C nanocomposites are synthesized using a high-energy, mechanical milling method with thermally synthesized Sn₂Fe, Al₂O₃ and carbon (Super P) powders. The effect of Al₂O₃ addition on the microstructure of the Sn₂Fe/Al₂O₃/C nanocomposites is examined. The electrochemical characteristics of the material as an anode in lithium-ion batteries are also evaluated. High-resolution transmission electron microscopy shows that the crystallite size of active Sn₂Fe in the Sn₂Fe/Al₂O₃/C nanocomposite is smaller than that of the Sn₂Fe/C nanocomposite without Al₂O₃. A decrease in the initial irreversible capacity and enhanced cycle performance of the Sn₂Fe/Al₂O₃/C nanocomposite electrode are observed.     

NiSb2 as negative electrode for Li-ion batteries: An original conversion reaction

The study of the electrochemical reaction mechanism of lithium with NiSb₂ intermetallic material is reported here. The nickel diantimonide prepared by classic ceramic route is proposed as possible candidate for anodic applications in Li-ion batteries. The electrochemical characterisation of NiSb₂ versus Li⁺/Li⁰ shows a reversible uptake of 5 lithium per formula unit, which leads to reversible capacities of 500 mAh g⁻¹ at an average potential of 0.9 V. From ex situ XRD and ¹²¹Sb Mössbauer measurements it was shown that during the first discharge the orthorhombic NiSb₂ phase undergoes a pure conversion process (NiSb₂ + 6 Li⁺ + 6e⁻ → Ni⁰ + 2Li₃Sb). During the charge process that follows, the lithium extraction from the composite electrode takes place through an original conversion process, leading to the formation of the high pressure NiSb₂ polymorph. This highly reversible mechanism makes it possible to sustain 100% of the specific capacity after 15 cycles.     

Synthesis and improved electrochemical performances of porous Li3V2(PO4)3/C spheres as cathode material for lithium-ion batteries

Spherical Li₃V₂(PO₄)₃/C composites are synthesized by a soft chemistry route using hydrazine hydrate as the spheroidizing medium. The electrochemical properties of the materials are investigated by galvanostatic charge-discharge tests, cyclic voltammograms and electrochemical impedance spectrum. The porous Li₃V₂(PO₄)₃/C spheres exhibit better electrochemical performances than the solid ones. The spherical porous Li₃V₂(PO₄)₃/C electrode shows a high discharge capacity of 129.1 and 125.6 mAh g⁻¹ between 3.0 and 4.3 V, and 183.8 and 160.9 mAh g⁻¹ between 3.0 and 4.8 V at 0.2 and 1 C, respectively. Even at a charge-discharge rate of 15 C, this material can still deliver a discharge capacity of 100.5 and 121.5 mAh g⁻¹ in the potential regions of 3.0-4.3 V and 3.0-4.8 V, respectively. The excellent electrochemical performance can be attributed to the porous structure, which can make the lithium ion diffusion and electron transfer more easily across the Li₃V₂(PO₄)₃/electrolyte interfaces, thus resulting in enhanced electrode reaction kinetics and improved electrochemical performance.     

Core/shell Fe3O4@Fe encapsulated in N-doped three-dimensional carbon architecture as anode material for lithium-ion batteries

Core-shell Fe₃O₄@Fe nanoparticles embedded into porous N-doped carbon nanosheets was prepared by a facile method with NaCl as hard-template. The three-dimensional carbon architecture built by carbon nanosheets enhance the conductivity of the encapsulated Fe₃O₄@Fe nanoparticles and strengthen the structure stability suffering from volume expansion during extraction and insertion of lithium ions. Rich Pores enhance the surface between electrode and electrolyte, which short the transmission path of ions and electrons. The core-shell structure with Fe as core further improves charge transferring inside particles thus lead to high capacity. The as-prepared Fe₃O₄@Fe/NC composite displays an irreversible discharge capacity of 839 mAh g^?1 at 1 A g^?1, long cycling life (722.2 mAh g^?1 after 500th cycle at 2 A g^?1) and excellent rate performance (1164.2 and 649.2 mAh g^?1 at 1 and 20 A g^?1, respectively). The outstanding electrochemical performance of the Fe₃O₄@Fe/NC composite indicates its application potential as anode material for LIBs.